Recent programs have investigated various aspects of the design and manufacture of advanced composite airframe structures for helicopters. Evaluation of the reliability and maintainability (R and M) and operating cost characteristics of the evolving design concepts has been limited, however. The objective of this program has been to assess the overall potential of advanced composite structures from the standpoint of R and M and life-cycle cost. A survey was made of in-service experience with helicopter airframe structures, concentrating particularly on bonded structures and composite materials. The surveys included visits to Army helicopter depots where typical types of damage were examined and discussed. A review was also made of published data on composites in use with fixed-wing aircraft. It was established that with the exception of some secondary structure, experience with composites in helicopter airframe applications is very limited, and that quantitative reliability factors cannot yet be established. However, it was concluded that the majority of failures with advanced composites will occur from external causes, primarily as a result of damage by impact.

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